Resilient materials



Patented i0,- 1945 UNITED STATES PATENT-Y OFFICE 2,371,710 assmsn'rMATERIALS I George Schneider, Montclair, N. J., and Mervin E.

Martin, Cumberland, MIL, assignorsto Celanese Corporation of America, acorporation of Delaware No Drawing.

Application November 12, 1941 Serial No. 418,861

3 Claims. 1 (Cl. 288- -34) This invention relates to the preparation ofresilient materials and relates more particularly to the. production ofresilient materials suitable for use as cushion liners in closures, suchas those 7 tureand internal pressure of the contents of the I containerson which they are applied.

Other objects of our invention will appear from the following detaileddescription.

Closures of various types are employed in sealing containers of glass ormetal which are used for holding liquids. In the case of carbonatedbeverages such as soft drinks, beer, etc., where it is important toretain the gas in solution, the closures are usually in the form of ametal cap or shell lined with a disc of some soft, easily deformablematerial which may be covered with a flexible metal foil. Theclosures'are put on the filled bottles-by a suitable capping devicewhich serves to bend the edges of the metal closure beneath a lipprovided at the top of thebottle and to force the soft, foil-covereddisc against the upper or pouring edge of the bottle. .The pressure ofthe disc against the bottle acts as a seal and serves to prevent the'bscape of either the gas or the liquid. Ordinarily, the soft disc isformed of a material such as cork, but the quality and availability ofthis materialvaries from time to time. For this reason, a suitablematerial having the physical advantages of cork but which is readily"available and whose quality can be controlled has long been sought.

be prepared from cellulose fibers insheet form, it the moisture contentof said material is main-- tained at a relatively high level. Inaccordance with our invention, cellulose fibers compocted into the formof a sheet or web are so treated as to incorporate therein a hygroscopicmaterial. and the sheet material then cut or shaped in any convenientmanner into discs or other shapes of suitabledimensions. The hygroscopicmaterial incorporated into the sheet material maintains the moisturecontent of the discs at the desired relatively high level and therebyimparts to the latter an unusual degree of resiliency. more preferably,after being faced with a film or foil of a suitable inert materialhaving a con- 10 tinuous structure. may then be used as cushion linersfor lining container closures. The film or .ioil protects the sheetmaterial from the action of the contents of the container. When theclosures are applied by a suitable capping delli vice, the cushionliners of our invention give.

a gasand liquid-tight seal which remains tight through wide fluctuationsin both the temperature and internal gas pressure of the container onwhich the closure is applied, as well as over extended periods ofservice.

Various hygroscopic materials may be employed for maintaining themoisture content of the cushion liners at the desired level and thehygroscopic materials, which may be liquid or solid, may be incorporatedinto said materials in many ways. The hygroscopic material may beincorporated into the cellulose fibers before they are formed intosheets, or the cellulose fibers may be treated after the'sheets havealready been formed. Preferably, the hygroscopic materials are appliedafter the fibers have already been fabricated into sheet form, or afterthe sheets have been cut or shaped into discs of the desired size. Inthis. way, the .amount incorporated therein may be more closelycontrolled and the moisture content may be maintained at any desiredpredetermined level by merely varying the relative amount of hygroscopicmaterial used. Preferably, the moisture content is maintained at from 25to by weight. Examples ofsuit- V able hygroscopic material which may beemployed are organic materials such as glycerine, glycols and sugars, orinorganic materials such as calcium chloride, magnesium chloride and 45.sodium nitrate. The materials are preferably applied in solution in asuitable solvent such as, for example-water or ethyl alcohol. Thehygroscopic materials may be employed in amounts varying from 15 to 50%on the weight of the 5 cellulose fiber sheet material, but more or lessmay be incorporated, as stated, depending upon the particulanmoisturecontent desired for the particular application of the cushion liner.

The film or toll employed for facing the cello-- I lose iiber cushionliner'm ay be a separate film The discs, when used alone, or

or toll cut to the desired size and then placed in osition, or the sheetmaterial may be coated with a solution of a material in avolatilesolvent which forms a film upon evaporation of said solvent. The film orfoil over the face of the cushion liner prevents the liquid in thecontainer from coming in contact with the cellulose fibers.

Examples of cellulose derivatives'which may be employed to form thefilms are cellulose esters such as cellulose acetate, celluloseropionate and cellulose butyrate, mixed esters such as celluloseacetate-propionate and cellulose acetate-butyrate, inorganic esters;such as cellulose nitrate, and

. cellulose others, such as for example, ethyl cellulose and benzylcellulose. Any suitable volatile solvent or mixture of solvents may beemployed in forming a coating composition suitable for coating the sheetmaterial used to form the cushion "liner. Solvents such as, for example,acetone, chloroform, ethylene dichloride, acetone and ethyl or methylalcohol, ethyl alcohol,and ethylene dichloride and ethyl or methylalcohol are suitable. j

The cellulose fiber cushion liner may be employed as a single layer ofthe desired thickness for'lining the metal closures, or the cushionliner may comprise a plurality of layers sumcient to build up a layer ofthe desired thickness. The layers may be held in position as by somebinding material or else the layers may be held in the metal closuremerely by the pressure exerted when the cap or shell is applied to acontainer.

In order further to illustrate our invention but withoutbeing limitedthereto the following examples are given:

Example I Discs of suitable size are cut or punched from a compactedsheet of wood pulp cellulose of about closure of the cap type inregister and faced with a cellulose acetate .fllm about 0.004 inch inthickness. The assembled closure is thenapplied to a bottle holding acarbonated beverage by means of a capping device. The sealed bottles arethen subjected to a pasteurization treatment during which the internalpressure rises from the usual 35 pounds per square inch to 100 poundsper square. inch. Oncooling, the pressure returns to 35 pounds persquare inch and remains there. The seal formed by the cellulose discremains permanently tight and there is .no loss in pressure due to theescape of gas. I

Exam le II Wood-pulp cellulose discs of proportions similar to those ofExample I are prepared, inserted into a bottle cap in register; andfaced by an unplasticized cellulose acetate film 0.004 inch inthickness, the whole system being cemented to-- and the resulting sealremains tight to gas and liquid under the varying conditions oftemperature and pressure during pasteurization as well as after.

It is to be understood that the foregoing detailed description is givenmerely by way or illustration and that many variations may bev madetherein without departing from the spirit of our invention.

to of an organic hygroscopic material selected from the group consistingof glycerine and diethylene glycol, and a facing of a preformed 4organic derivative of cellulose foil secured to said a material.

2. A resilient material adapted to be employed to form a pressure seal,comprising a compact material in sheet formhaving a basis of woodpulpcellulose fibers and having incorporated therein an aqueous solutioncontaining from 15 to 50% of an organic hygroscopic material seiectedfrom the group consisting of glycerine and dlethylene glycol, andafacing of a preformed cellulose acetate foil securedtosaid material.

3. A resilient material adapted to be employed to form a pressure seal,comprising a compact material in sheet form having a basis of, wood.-

pulp cellulose fibers and having incorporated therein an aqueoussolution containing 50% of an organic hygroscopic materialselected fromthe group consisting of glycerine and diethylene lycol, and is facing ofa preformed cellulose acetate foil secured to saidmaterial.

- GEORGE SCHNEIDER.

